Image forming systems which exhibit photographic characteristics of ultra-high contrast (especially those of gamma (.gamma.) at least 10) are required to improve the reproduction of continuous gradation images by means of a screen dot image or to improve the reproduction of line images in the graphic arts field.
There is a demand for image forming systems with which ultra-high contrast photographic characteristics are obtained with development with a developer which has good storage stability. There is also a demand for methods in which surface latent image type silver halide photographic photosensitive materials to which specified acylhydrazine compounds have been added are processed in a developer of pH 11.0 to 12.3 which contains at least 0.15 mol/liter of sulfite preservative and negative images of ultra-high contrast with gamma exceeding 10 are formed. Systems of this type have been suggested in U.S. Pat. Nos. 4,166,742, 4,168,977, 4,221,857, 4,224,401, 4,243,739, 4,272,606 and 4,311,781. These new image forming systems are distinguished by allowing the use of silver iodobromides and silver chloroiodobromides, rather than only allowing the use of silver chlorobromides which have a high silver chloride content as in the case of conventional ultrahigh contrast image formation systems. Furthermore, it is possible to use a large amount of sulfite preservative, instead of only the very small amount of sulfite preservative which is possible in conventional lith developers, and so there is the further distinguishing feature that storage stability is comparatively good.
However developers of pH 11 or above are susceptible to aerial oxidation and are unstable, and they cannot endure long term storage or use.
Means of forming high contrast images by developing silver halide photosensitive materials which contain hydrazine compounds in a developer of lower pH have been investigated.
Methods of processing with development in a developer of pH 11.0 or below using sensitive materials which contain nucleation development accelerators which have groups which are adsorbed onto silver halide grains, or nucleating agents which have similar adsorbing groups, have been disclosed in JP-A-1-179939 and JP-A-1-179940. (The term "JP-A" as used herein signifies an "unexamined published Japanese patent application".) However, the emulsions used in these inventions are of silver bromide or silver iodobromide, and there is considerable variation in photographic performance resulting from changes in the composition of the developer and development progression, and they cannot be said to be satisfactory in terms of stability.
Hydrazine compounds which have ethylene oxide repeating units and hydrazine compounds which have pyridinium groups have been disclosed in U.S. Pat. Nos. 4,998,604, 4,994,365 and 4,975,354. However, according to the illustrative examples given, the high contrast is inadequate in these inventions and it is difficult to obtain the D.sub.max and a required high contrast under practical development conditions.
Furthermore, nucleation high-contrast materials in which hydrazine derivatives are used exhibit a very wide variation in photographic properties depending on fluctuations in the pH of the developer. The pH of the developer fluctuates widely, being increased by the aerial oxidation of the developer and concentration due to the evaporation of water, and being reduced by the absorption of carbon dioxide from the air. Hence, means of minimizing developer pH dependence of photographic performance have also been investigated.
Examples of the use of chemically sensitized silver chlorobromides in systems in which hydrazines are used have been disclosed, for example, in JP-A-53-20921, JP-A-60-83028, JP-A-60-140399, JP-A-63-46437, JP-A-63-103230, JP-A-3-294844, JP-A-3-294845, JP-A-4-174424 and Japanese Patent Application No. 3-188230. On the other hand, examples in which hydrazines are used conjointly with silver halide emulsions which contain heavy metal complexes, such as rhodium or iridium complexes, have been disclosed, for example, JP-A-60-83028, JP-A-61-47942, JP-A-61-47943, JP-A-61-29837, JP-A-62-201233, JP-A-62-235947 and JP-A-63-103232.
Cases in which colloidal silica and polyacrylamide derivatives are included in systems in which the hydrazine is used have been disclosed in many patents such as JP-A-61-140939, JP-A-1-156734 and JP-A-4-214551.
Many cases of the inclusion of cyanine dyes which have an anionic charge, starting with the alkali salts of 5,5'-dichloro-9-ethyl-3,3'-bis(3-sulfopropyl)-oxacarbocyanine, in systems in which hydrazine is being used have been disclosed, such as those disclosed, for example, in JP-A-61-29837, JP-A-62-235947, JP-A-62-280733, JP-A-62-280734, JP-A-2-40, JP-A-2-124560, JP-A-2-262653 and JP-A-3-63641.